1. Place the vehicle on a lift or inspection ditch, clean the pressure regulator and protective cover from dirt.
2. Carefully remove the protective cover from the pressure regulator, remove any remaining grease and clean the connection «torsion piston».
3. Ask an assistant to press the brake pedal with a force of 686–784 N (70–80 kgf) and at the same time observe the protruding part of the pressure regulator piston.
4. If the piston moves relative to the pressure regulator body by 0.5–0.9 mm, while twisting the torsion lever, then the pressure regulator is operational. Repeat pressing the pedal 2-3 times to fully verify that the pressure regulator is working.
5. If the piston remains stationary when the pedal is depressed, indicating that the piston is stuck to the body, then replace the pressure regulator.
6. After making sure that the pressure regulator is working and that there is no leakage of brake fluid between the piston and the pressure regulator housing, cover the axis and the protruding part of the piston with a layer of grease DT-1, put 5–6 g of this grease in a rubber boot and install the boot in place.